Cam motion transmitting device



March 28, 1939. I E BUGATTl 2,151,832

' CAM MOTION TRANSMITTING DEVICE Filed Sept 16, 1955 Patented Mar. 28,I939 Q'UN ITED STATES "PATENT OFFICE 7 2,151,832 CAM MOTION TRANSMITTINGDEVICE Ettore Bugatti, Molsheim, France Application September 16, 1935,Serial No. 40,831 In France September 21, 1934 7- Claims.

' exists, between said roller and its spindle, a certain play a, due towear, and tear, the distance between the axis of the cam and the axis ofthe spindle'is modified and varies according to the relative position ofthe cam. Consequently, the law of displacements of the controlled memberas a function of the angular position of the cam is modified and greatlyperturbed. This drawback becomes extremely important if the alterationsthus brought about in the displacements of the member controlled by thecam result in magnified alterations caused in the operation of deviceswhich are actuated or operated by said member. This is the case when thecam controls the upward movement of a valve through which takes placethe inflow of a fiuid under pressure.

The object of the present invention is to provide an improved mechanicaltransmission through a cam which obviates or at least reduces thedisadvantages above stated. The essential feature of the presentinvention consists in doing away with the spindle of the roller and inarranging said roller in such manner that it rests through its peripheryon other rollers, these last mentioned rollers being mounted in theusual manner on the driven member.

Owing to this arrangement, the play that may occur between thesupplementary rollers and their spindles modifies the displacements ofthe driven member only by an amount which does not vary or does not varysubstantially throughout a revolutionof the cam; owing to the use of twoor more auxiliary rollers, each auxiliary roller is less subjected towear so that the above named amount is generally small and in any casecan be easily taken up by reason of its being constant throughout arevolution of the cam. Furthermore, the forces that are transmitted tothe rollers added according to the present invention act on each of themin a fixed direction, their only variations being variations ofamplitude.

Other features of the present invention will result from the followingdescription of some specific embodiments thereof.

Preferred embodiments of the present invention will be hereinafterdescribed, with reference 'to the accompanying drawing, given merely byway of example, and in which: i 1 Fig. 1 diagrammatically shows a knowntransmission applied to the vertical reciprocating displacement of amember;

Fig. 2 shows a transmission ensuring the same movement according to thepresent invention;

Figs. 3 and 4 diagrammatically show two rocker arms, according to theinvention, respectively, together with the cams through which they are"5 actuated;

Figs. 5 and. 6 are sectional views, on an enlarged scale, of two otherembodiments of the invention.

With a view to simplifying the description of 10 the invention, I haveshown, in Figs. 1 and 2, a

- member I, which may be any member whatever of a mechanical structure,said member I being actuated by a cam 2, through a roller 3, in suchmanner as to have a vertical reciprocating dis- 15 placement.

Fig. 1 shows the usual arrangement, in which roller 3 is carried by apivot or spindle. 4 provided on member i. Supposing that said spindle 4has been worn uniformly over its periphery,'so that 20 the reduction ofits diameter is 2a, this value -being shown with a considerableexaggeration on the drawing, the upward displacement of member l isreduced by an amount which depends upon the angle a, if a is the anglemade by a line 25 passing through the center of pivot 4 and through thepoint of contact of roller 3 and cam 2 with a line passing through therespective centers C and C1 of cam 2 and pivot 4. This angle varies, inthe course of a revolution of the cam, between 30 'zero and one orseveral maxima. Consequently,

it is not possible, by means of a packing piece of determined thicknessor any other mechanically equivalent means, to take up the existingplay, and if, for instance, member I serves to .35 cause the opening ofa valve, the adjustment of the flow of fluid past said valve is whollydestroyed, without any possibility of restoring said I adjustment.

In its simplest form, the device according to 40 the invention consists,as shown in Fig. 2, in the provision of at leasttwo rollers 5, '6,preferably disposed symmetrically with. respect tothe line of therespective centers of the main roller and the cam, said rollers 5, 6being supported by pivots 45 I, 8 and replacing the pivot of roller 3.Said roller 3 is attached to member I through any suitable means. 7

As there. are two rollers, 5 and 6, for guiding roller 3, their wear isobviously smaller than that, 50 of spindle 4 in Fig. 1. Although theeffort of cam 2 on roller 3 is always exerted at a point more or lessremote from line C 01, roller 3 remains constantly applied againstrollers 5, 6 if said last mentioned rollers have been placedsufficiently Wide apart from each other, so that only the magnitude ofthe components of this effort along lines C102 and C103 varies.Consequently, if p is the angle of ClCZ of C103 with C C1, themodification of the position of members depends upon the angle 13, butis the same for all the positions of said member since the angle 3 doesnot vary during a revolution of the cam 2. Generally, the angle ,8 canbe given a relatively high value. Thus, owing to the arrangementaccording to the present invention, the variation of position of themember driven by the cam for a play equal to 2a between the auxiliaryrollers and their support is uniform.

When the driven member is a pivoting one such as a rocker arm 9actuating a valve stem, for instance in the vertical direction, themodification in the position of center Cl, other things being equal, hasa uniform value, it being still supposed that both rollers areidentical. Due to the fact that angle 13 is relatively large and thatthe wear of the rollers is reduced since the effort exerted by the camis divided between them, the displacement of the center C1 of the rolleris always very small and as this roller is generally,

located at a relatively great distance from the axis Ill of the rockerarm, the alteration produced in the rocking displacements of the arm 9is small and therefore easy to remedy.

Of course, the distance between the auxiliary rollers 5, 6 and theirdiameter must be chosen in such manner that roller 3 has no tendency tolose contact with them as a consequence of the obliquity of the thrustof the cam, and, on the other hand, that there is no risk of wedging.

In order to connect roller 3 with the rocker arm or any other drivenelement, I may make use of any device capable of ensuring the requiredfreedom of movement of said roller while preventing it from dropping orotherwise escaping when the rocker arm is assembled or removed. Such adevice may consist of a setting arrangement, a plate ll provided with anaperture of suitable size, an elastic connection, etc. I may even leavea pivot or spindle for the roller, provided that said spindle servesonly to prevent the roller from dropping when no longer in contact withthe cam. In other words, and according as the case may be, the pivot orspindle extends, with a considerable play, through a central hole of theroller, or, if it is rigid with the roller, through holes provided inthe driven element.

Owing to the fact that roller 3 is no longer guided by a pivot orspindle, it is possible to reduce to a minimum the diameter of thisroller, in which case it is easier than with an ordinary roller to makeuse of cams the outline of which includes concave portions, such as caml2 of Fig. 4. If a larger roller were employed, it might bridge theedges of the depression in the cam.

The roller may be replaced by'a ball 13, as shown in Fig. 5, in whichcase the auxiliary rollers I4 have an outline corresponding to that ofthe ball, as shown by the drawing.

The roller may also have a conical shape, as shown at IS in Fig. 6. Inthis figure, one of the auxiliary rollers with which roller [5cooperates is visible at l6.

The cams I! that are shown in Figs. 5 and 6 are shaped in such manner asto permit an adjustment of the lift of the valves which are driven bythe device by moving the cams in the direction of their geometrical axisof revolution.

In a general manner, while I have, in the above description, disclosedwhat I deem to be practical and eflicient embodiments of the presentinvention, it should be well understood that I do not wish to be limitedthereto as there might be changes made in the arrangement, dispositionand form of the parts without departing from the principle of thepresent invention as comprehended within the scope of the accompanyingclaims.

What I claim is:

1. In a mechanical motion transmitting device having a cam controlledmovable member and an actuating cam therefor, the combination of atleast two spaced apart rollers, means for pivotally mounting saidrollers on the movable member about substantially parallel, spaced apartaxes, a floating, rolling element interposed between the cam and therollers, adapted in operation to have tangential rolling contact withsaid rollers, and means for retaining the rolling element in a floatingposition on the movable member in abutting relationship with saidrollers, the said cam cooperating with said floating element.

2. In a mechanical motion transmitting device having a cam controlledmember movable along a predetermined path and a cam for actuating saidmember, the combination of two spaced apart rollers, means for pivotallymounting said rollers on the cam controlled member about substantiallyparallel axes spaced apart in a plane substantially at right angles tosaid path, a floating, rolling element interposed between the cam andthe rollers, adapted in operation to have tangential rolling contactwith said rollers, and means for retaining the rolling element in afloating position on the movable member in abutting relationship withsaid rollers, the said cam cooperating with said floating element.

3. In a mechanical motion transmitting device having a cam controlledmember movable along a predetermined path and a cam for actuating saidmember, the combination of two substantially parallel, spaced apartpivot pins mounted on the cam controlled member in a plane substantiallyat right angles to said path, a roller on each pivot pin, a floating,rolling element held on the cam controlled member adapted, in operation,to have tangential rolling contact both with the two rollers and thecam, and means for retaining the rolling element in a floating positionon the movable member in abutting relationship with said rollers, thesaid cam cooperating with said floating element.

4. In a mechanical motion transmitting device having a cam controlledmovable member and an actuating cam therefor, the combination of at Aleast two spaced apart rollers; means for pivotally mounting saidrollers on the movable member about substantially parallel, spaced apartaxes; a rolling, floating cam-engaging element interposed between thecam and the rollers to have tangential rolling contact with saidrollers; and means on said movable member for positively limiting thedisplacement of the rolling element away from the rollers.

5. In a mechanical motion transmitting device having a cam controlledmovable member and an actuating cam therefor, the combination of atleast two spaced apart rollers; means for pivotally mounting saidrollers on the movable member about substantially parallel spaced apartaxes; a rolling element having a noncylindrical periphery, interposedbetween the cam and the rollers, the latter having noncyclindricalperipheries complementarily shaped with respect to that of the rollingelement for engagement in.

tangential rolling contact therewith; and means for retaining therolling element in a floating position on the movable member in abuttingrelationship with said rollers, the said cam cooperating With saidfloating element.

6. In a mechanical motion transmitting device having a cam'controlledmovable member and an actuating cam therefor, the combination of twogrooved, spaced apartrollers; means for pivotally mounting said rollerson the movable member about substantially parallel, spaced apart, axes aball interposed between the cam and the grooved rollers, adapted inoperation to fit in both rollers simultaneously, in tangential rollingcontact therewith, and means for retaining the ball in a floatingposition on the movable member in abutting relationship with saidgrooved rollers, the said cam cooperating with said floating element.

'7. A mechanical motion transmitting device which comprises a movablemember, at least two spaced apart rollers; means for pivotally mountingsaid rollers on said movable member about substantially parallel, spacedapart axes, a control cam the cross section of which varies graduallyalong its axis, a floating rolling element interposed between the camand the rollers for imparting motion from said cam to said member,adapted in operation to have tangential rolling contact with saidrollers, and means for retaining the rolling element in a floatingposition on the movable member in abutting relationship withsaid'rollers, the said cam cooperating with said floating element.

ET'I'ORE BUGATTI,

